removable presta core; pump won't seal

keef66

Son has acquired a neglected but functional mid 80's Peugeot. On attempting to inflate the tyres I found my road morph pump head wouldn't seal on the valves. Closer inspection and comparison with the valves on my bike showed that the reason was the removable cores. They have flats on the short threaded part presumably to facilitate removal / tightening using a small spanner, and I'm assuming this is the bit the pump head rubber seal is not making good contact with.

Would a proper track pump seal any better? Would it go further down the valve and grip / seal against the longer threaded portion? Or should I go for the easy option and bin the tubes in favour of some I can inflate with my pump??

Rodrego Hernandez

If the tubes are from the mid-80s then definitely get some new ones. Non-threaded valves give a better seal around a pump head if you can get some . Michelin are not threaded I think.

It is air pressure that opens the valve, not the pump pressing the valve.

keef66

I don't think the tubes and tyres are the originals, they look in much better nick than the rest of the bike. Maybe I'll take a tube into the LBS and see if their track pump works on it.

sungod

i've never had a problem getting a pump to work with removable cores, is it possible the seal on the pump is worn?

keef66

TBH it is possible. I've been using it as my one and only pump for over 2 years. Still works on my Conti tubes / valves though.

I get the feeling that not enough of the valve is going inside the rubber bit in the pump head.

Should it be sealing against the short threaded bit that the valve cap is screwed on to, or the longer threaded bit that goes all the way to the rim? I think I've only been doing the former. Should I have to really press hard on the pump head when fitting it onto the valve before locking it on? I have studied the locking action, and the rubber insert is squashed as the lever is raised so I'm doing that bit right

sungod

my track pump goes over the main body of the valve stem, so the actual core is deep inside the head

my mini pump is a lezyne one with a hose that screws onto the core thread, there's a rubber seal inside that i think hits the stemto seal it

i've used another mini pump as well, it just pushed on, not sure of the brand, but it was ok too

as you say, maybe you need to push it on further/harder to get a seal

otherwise you could try putting a bit of insulating tape around the thread to give a better seal, but probably simpler in the long run to get some new tubes with fixed cores

keef66

In the end I did get it to seal by pushing it further on, but came to the conclusion the tube was past it cos it was deflating as fast as I pumped. New tubes it is then!

And possibly a track pump in the sales.